February 14, 2007

How Reliable Are the Early Presidential Polls?

by Nilanthi Samaranayake and Scott Keeter

The flurry of candidate announcements in an open race has spurred media attention to the 2008 presidential contest even earlier in the electoral cycle than usual. But followers of early poll readings on the relative viability of declared candidates should bear in mind some caveats. Early frontrunners for the Republican nomination in most of the past seven open contests have gone on to win the nomination, but this year there is not one but two GOP frontrunners. On the Democratic side, even when there is a clear frontrunner as there is this year with Sen. Hillary Clinton, the early polls have been less reliable in predicting who will capture the nomination.

Moreover, the past polling history may be less relevant today. The process is starting earlier than ever this year and while there are some well known contenders, the public’s level of familiarity with the overall field of candidates is still very low. And the increased front-loading of the primaries and the growing importance of early fundraising means that the dynamics of the nominating process are apt to be somewhat different this election cycle, making comparisons with past elections less useful.

It’s not just the case that polling in the nominating contests is perilous. Polls that test hypothetical general election matchups at this stage in the cycle are mostly wrong about who will win the White House. Early polling does provide a benchmark for charting trends in voter sentiment, but it probably won’t be very predictive of the eventual outcome in 2008.

Early Leads in the Nominating Process

FigureStill, with the nominating conventions more than 17 months away, what, if anything, do these early polls mean for would-be nominees? A look back at nearly 50 years of early primary polls suggests that Republican front-runners are often a good bet to capture the nomination, but the picture is more mixed for leading Democrats.

In seven open Republican contests since 1960, the early front-runners held on to win the party nod six times.1 By contrast, early Democratic poll leaders won four out of eight open contests between 1960 and 2004. In early 2003, Sen. John Kerry was tied with Sen. Joseph Lieberman, but fell behind Gen. Wesley Clark and Vermont Gov. Howard Dean at different times later in the year before eventually getting the final nod from Democrats.

Unfortunately for Republican aspirants in this cycle, no candidate can benefit from the GOP’s traditional early leader tenacity for the simple reason that no single frontrunner has been established. Until recently, former New York mayor Rudy Giuliani and Sen. John McCain had been running neck-in-neck in Republican horse race polls. Although recent nationwide polls show Giuliani slightly outpacing McCain among likely GOP primary voters, some election watchers are skeptical about Giuliani’s chances, given his relatively liberal views on social issues.

On the other hand, the Democratic front-runner, Clinton as of now, need not necessarily be daunted by historical precedent, whatever other challenges she may face in the months to come. At least two of the Democrats who did not win the nomination withdrew from the race for reasons other than lagging support in the polls. One decided against a run (New York Gov. Mario Cuomo in 1992); one withdrew in the face of scandal (Sen. Gary Hart in 1988).

Wobbly General Election Polls

FigureEarly general election presidential trial heat polls have a poor track record. History suggests the political climate is almost certain to change between now and November 2008.

A review of polls conducted in the first quarter of the year preceding the election found many of them forecasting the wrong winner — often by substantial margins. In February 1995, several early readings showed Sen. Bob Dole leading President Bill Clinton by as many as 6 percentage points. Twenty-one months later, Clinton won by 8 percentage points. In March 1991, President Bush had the support of 78% of the electorate against Democrat Mario Cuomo, the New York governor then perceived as the Democratic frontrunner. Bush lost to Clinton by 6 percentage points in 1992.

Those instances in which the polls did accurately forecast the winner represent a mixed bag of candidates and electoral circumstances. Polls in March 1967 placed former Vice President Richard Nixon neck-in-neck with President Lyndon Johnson, with the public split 48%-48% between them; the final popular vote was 43% for Nixon, 43% for the Democratic nominee Hubert Humphrey. However, Nixon benefited from being familiar to the general public for his eight years as vice president, unlike most presidential candidates who are relatively unknown to the national public at that stage in an election cycle.

Four years later, a poll gave President Nixon a slim 43%-39% lead over Sen. Edmund Muskie in March 1971. While the poll correctly predicted that Nixon would win, his margin of victory over the actual Democratic nominee, George McGovern, was a whopping 23 points.

Conversely, in the run-up to the 2000 election, early 1999 polls showed Texas Gov. George W. Bush with a wide lead over Vice President Al Gore. Bush won the election in the Electoral College but lost the popular vote.


Notes

1Early front-runners are candidates who drew the strongest support among all potential nominees in national polls taken more than a year before the presidential election. Questions about Republican nominees were typically asked of Republicans and Independents who lean Republican; questions about Democratic nominees were typically asked of Democrats and Independents who lean Democratic. Data are drawn from Pew Research Center, Gallup, Harris, and CBS News/New York Times surveys.